Ripl radio interferometric planet search
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RIPL Radio Interferometric Planet Search. Geoffrey Bower UC Berkeley. Collaborators: Alberto Bolatto (UMD), Eric Ford (UFL), Paul Kalas, Anna Treaster, Vince Viscomi (UCB). MM Wavelength T Tauri Outburst in Orion. 2 nd most luminous stellar radio outburst

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RIPL Radio Interferometric Planet Search

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Ripl radio interferometric planet search

RIPLRadio Interferometric Planet Search

Geoffrey Bower

UC Berkeley

Collaborators: Alberto Bolatto (UMD), Eric Ford (UFL),

Paul Kalas, Anna Treaster, Vince Viscomi (UCB)


Mm wavelength t tauri outburst in orion

MM Wavelength T Tauri Outburst in Orion

  • 2nd most luminous stellar radio outburst

  • Briefly, brightest object in nebula

  • Required long baselines for detection

  • Magnetized T Tauri outburst

  • Contemporaneous with X-ray outburst

  • Many such objects likely to be found by CARMA & ALMA

BIMA A configuration images

(Bower, Plambeck, Bolatto, Graham, de Pater, McCrady, Baganoff 2004)


Orion nebula parallax w star gmr a

Orion Nebula Parallaxw/Star GMR-A

D=389 pc +/- 5%

<0.1 mas/epoch

Sandstrom, Peek, Bower, Bolatto,

Plambeck 2007

Astro-ph/0706.2361


Planets are easy to detect

Planets are Easy to Detect


Companion to gj 752b detected w optical astrometry

Companion to GJ 752B Detected w/Optical Astrometry

Pravdo & Shaklan 2009


Ripl radio interferometric planet search

White et al


Ripl radio interferometric planet search

Gudel 2002


Requirements of a planet survey

Requirements of a Planet Survey

  • Low mass, nearby star

    • Astrometric displacement ~ 1 mas

  • Nonthermal radio emission

    • S ~ 1 mJy

    • F ~ GHz

    • Positional stability < 0.1 mas

  • Stable Image

    • Active, but not too active


Vla m dwarf flux survey

VLA M dwarf Flux Survey

  • 174 X-ray selected nearby M dwarfs

  • 10 minute VLA observations with 50 microJy rms

  • 40 detections of 29 stars

  • Rough agreement X-ray-radio correlation

  • No distinction between early and late types

Bower, Bolatto, Ford, Kalas 2009, ApJ, in press


Stars are variable

Stars are Variable

EV Lac

Osten et al 2005


Pilot survey

Pilot Survey

  • 7 stars

  • 3 epochs

  • < 10 days

    • Hipparcos errors ~ 1 mas/y

    • Error over 10 days < 0.1 mas

  • Test

    • Detectability

    • Image stability

8000 km baselines

3 cm wavelength

1 mas resolution

Astrometry ~ beam/SNR


Results from pilot study apparent motion of gj 4247

Results from Pilot Study:Apparent Motion of GJ 4247

15 mas

26 March 2006

25 March 2006

23 March 2006

Comparison of radio positions (points) with predictions from Hipparcos astrometry (solid line) reveal noise-limited rms residuals ~0.1 milliarcseconds, approximately 1 stellar diameter.

Bower, Bolatto, Ford, Kalas 2009, ApJ, in press


Pilot study results

Pilot Study Results

GJ 4247

GJ 896A

Residuals are sensitivity limited

~0.2 mas

GJ 65B


Vpas results

VPAS Results


Results from pilot study constraints on companion masses

Results from Pilot Study:Constraints on Companion Masses

Planet Mass (Mjup)

Semi-major Axis (AU)

  • Agreement with optical astrometry sets upper limit on acceleration and therefore companion masses

    • Mp < 3 – 10 MJup @ 1 AU

  • Sensitivity is limited by the short lever arm of VLBA observations: ~10 days

  • RIPL will extend this lever arm by factor of 100

Bower, Bolatto, Ford, Kalas 2009, ApJ, in press


Ripl radio interferometric planet search1

RIPLRadio Interferometric Planet Search

  • 30 stars

  • 12 epochs/4 years

  • VLBA + GBT

  • 512 Mb/s

  • 2 hours on source + 2 hours calibration

  • 25 microJy rms

    • 4 x lower than pilot survey

  • 1392 hours total

Key question: What is fraction of long-period planets around low mass stars?


Ripl sample

RIPL Sample

  • 30 Stars

  • M1 – M8

  • V = 9.6 – 15.8 mag

  • S_6cm = 0.1 – 6 mJy

  • D = 2.7 – 9.5 pc

  • 11 are members of known binary or multiple systems


Simulated ripl results

Simulated RIPL Results


Ripl sensitivity

RIPL Sensitivity


Current status

Current Status

  • Observing began Oct 2007

    • Approximately 4 observations/month

  • Expected completion in mid-2011

  • 40% complete

  • Pipeline processing underway (see poster by Vince Viscomi)

  • All stars detected

    • 60% of stars detected in every epoch


Benefits of astrometric detection

Benefits of Astrometric Detection

  • Unique method

  • Breaks degeneracy of RV searches for mass, inclination angle, and ascending node

  • Probes low mass, active stars that are difficult to study with RV method

  • Planet fraction of low mass stars poorly determined

  • Detects planets that can be studied with extreme AO

  • Ties radio and optical astrometric reference frame


Rv search results few m dwarf hosts

RV Search ResultsFew M dwarf Hosts


Rv search results most planets are 10 pc distant

RV Search ResultsMost Planets are >10 pc Distant


Rv search results what is mplanet mstar

RV Search ResultsWhat is Mplanet/Mstar?


Microlensing search results what is mplanet mstar

Microlensing Search Results What is Mplanet/Mstar?


Microlensing search results planets are very distant

Microlensing Search ResultsPlanets are Very Distant


Comparative sensitivity of searches

Comparative Sensitivity of Searches


Future directions for radio astrometry planets

Future Directions for Radio Astrometry & Planets

  • Bandwidth upgrade for VLBA

    • 512 Mb/s  8 Gb/s

    • 4 x sensitivity

    • Calibrator density increases by 8 x

    • In-beam calibrators

    • 10 microarcsec accuracy  Neptune mass planets

  • Square Kilometer Array

    • 100 x sensitivity

    • 3000-5000 km baselines

    • 1 microarcsec accuracy  Earth mass sensitivity


Summary

Summary

  • Radio astrometry is sensitive to sub-Jupiter mass planets around M dwarfs

  • We can already exclude BD companions to three stars based on only three measurements

  • RIPL survey will probe low mass, active star parameter space


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